I don't think you can pump carbon dioxide into the atmosphere indefinitely and not have a reaction. But there are great scientists such as Freeman Dyson, one of the greatest physicists of the last hundred years, who has studied the question, who believes quite the opposite. The reason transnational action is so difficult is because the major problem with climate change is, A, that there is no consensus, and, B, that the economic cost is simply staggering. Reversing it completely might mean undoing the modern industrial economy.

Americans are not intrinsically imperial, but we ended up dominant by default: Europe disappeared after the Second World War, the Soviet Union disappeared in 1991, so here we are.

Why should we care about the coup? First, because we depend on Yemen's government to support our drone war against another local menace, al-Qaeda in the Arabian Peninsula (AQAP). It's not clear if we can even maintain our embassy in Yemen, let alone conduct operations against AQAP. And second, because growing Iranian hegemony is a mortal threat to our allies and interests in the entire Middle East.

Clashes of values and the struggle for primacy constitute a constant in human history that accounts for that other constant - conflict and war.

Tuesday's victory was big. But it did nothing more than level the playing field and give you a shot. Take it.

If fences don't work, why is there one around the White House.

I don't mind going into a liberal lion's den. That's where you test yourself.